Automatic motor starter



Dec. 11, 1923. 1,477,405

L. J. WEBER ET AL AUTOMATIC MOTOR STARTER Filed April 14, 1921 ,fnvntor-st Louis J. \Xbber; Ernest C. Gooch,

yCZfl Their- Attorney.

Patented Dec. 11, 1923.

UNITED STATES PATENT OFFICE.

LOUIS J. WEEK OI SCOTIA, NEW YORK, AND ERNEST C. GOOCH, OI ESTES PARK, COLORADO, ,ASSIGNOBS TO GENERAL ELECTRIC COMPANY, A CORPORATION 01' NEW YORK.

auroma'rrc moron s'ran'rm.

application ma April 14, 1921. Serial No. 461,190.

To all whom it may concern:

Be it known that we, LOUIS J. Wanna and ERNEST C. Gooon, citizens of the United States, residing, respectively, at Scotia, count of Schenectady, State of New York, and stes Park, county of Larimer, State of Colorado, have invented certain new and useful Improvements in Automatic Motor Starters, of which the following is a specification.

Our invention relates to the control of electric motors, and it provides improved means whereby the motors are automatically accelerated under the control of the motor current.

A common arrangement heretofore used for controllin the automatic starting of a motor under t e control of the motor current has involved the use of a current limit relay having a switch member which is normally held in one position and movable under the control of the motor current to a second position to energize an electromagnetic accelerating switc These former arrangements have not always been entirely free from objection due to the fact that when the motor current drops to somewhere near the value at which it is intended that the switch member shall energize the accelerating switch, the switch member is apt to alternately make and break the circuit controlled by it and thereby cause severe arcin and burning of the contacts. One of the o jects of our invention is to prevent this destructive action of the contacts. In carrying our invention into eflect in one form, we provide an electromagnet energized in the second osition of the switch member for ositively olding it in that position when t e motor current first drops to the predetermined value. The arrangement is. preferably such that the switch member is never called upon to break a circuit, so that the contacts controlled by the switch member are relieved of all amin and burning.

For a better understanding of our invention, reference is had to the accompanying drawing showing in very simplified diagram a system of motor control embodying our invention for purposes of illustration.

Referring to the drawing, the electric motor 10 having the resistors 11 in its rotor circuit is ada ted to be connected to the source of supp y 12 by means of the electromagnetic switch or contactor 13. The accelcrating contactor 14 is provided for short clrcuiting the resistors 11 in therotor circuit when the current taken by the motor has dropped to the predetermined value after the closing of the starting switch 13. The contactor 14 is controlled by means of a current limit relay 15. Th1s relay comprises a switch member 16 biased to its lower position and mechanically held in its upper position (that shown in the drawing) by means of the plunger 17 of a controlling electromagnet ener 'zed responsively to the current taken b t e motor. This plunger 17 is mechanical y held in its upper position by means of the plunger of a releasing electromagnet 18, operating through the lever '19, the arrangement belng such that when the electromagnet .18 is energized, the plunger 17 is permitted to drop under the control of the motor current and thereby permit the switch member 16 to drop to its second position. The electromagnet 20, having a winding with a relatively low' resistance as compared to the winding of the electromagnet 18 and the winding of the accelerating contactor 14, is provided for holding the switch member in the second position when the motor current, has first dro pod to the value at which the switch mem ber 16 first makes engagement with the stationary contact 21. A master switch 22 is provided for controlling the arrangement at will.

As thus constructed and arranged and with the various parts in the positions shown in the drawin the operation of our invention is as fol ows:--

Turning the master switch to the position at which its segments make engagement with their respective contacts, the winding of the contactor 13 is energized across one of the phases of the source of supply 12. The contactor 13 is provided with an auxiliary switch 23 which is closed in the closed position of the contactor, and the electromagnet 18 is energized through this auxiliary switch and the normally closed auxiliary switch 24 associated with the contactor 14, the circuit being from the middle su ply conductor through the lowest segment 0? the master switch 22, the winding of contactor 14, auxiliary switch 24, auxiliary switch 23, through the winding of electromagnet 18 to the lower suppl conductor. The res tive resistances of t e windings of the e ectromagnet 18 and of the oontactor14 are of such relative values that the contactor 14 will not be energized to close, but the electromagnet 18' will be energized to pick up its plunger and thereby release the plunger 17 to drop under the control of the motor current when the motor current first drops to the predetermined value. W hen this happens, the switch member 16 will drop to its second position to make engagement with the stationary contact 21. The winding of electromagnet 18 will then be shunted by the winding of the holding electromagnet 20, and the holding electromagnet will be energized to hold the switch member and prevent it from vibrating. This vibrating may be due to the chattering which is experienced with alternating current switches or may be due to the fact that when the switch member 16 makes engagement with the contact 21 the winding 18 is shunted and thereby deenergized, causing the switch member to be raised. The winding of electromagnet 20 is of considerably lower resistance than the winding of electromagnet 18, and the contactor 14 will thereby be energized to close. In the closed position of the contactor 14, the contactor will be maintained energized through an auxiliary switch 25, and the auxiliary switch 24 will open the circuit of the electromagnets 18 and 20. The winding of the contactor 14 is energized through a circuit from the middle supply conductor, the lower segment of the master switch 22, through the auxiliary switch 25 to the lower supply conductor. The deenergization of the electromagnets 18 and 20 will cause the various parts of the relay 15 to return to their original positions, those shown in the drawing. The relay is therefore in proper position to again efiect the automatic closing of the contactor 14 when it is desired to start the motor again. It will be observed that inasmuch as the auxiliary switch 25 of the contactor 14 makes engagement with its contacts before the auxiliary switch 24 breaks engagement with its contacts, that the switch member 16 of the current limit relay is never required to open a circuit. Burning and pitting of the relay contacts due to arcing is thereby prevented.

In order to stop the motor, it will be understood that the master switch 22 shall be returned to the position shown in the drawing. It will also be understood that in case the master switch is merely turned to its first position, the accelerating cont-actor 14 will not be energized, or if the contactor 14 has been energized that it will be deenergized by returning the master switch from its second position to its first operative position.

In acordance with the provisions of the patent statutes, we have described the principle of operation of our invention, together with the apparatus which. we now consider to represent the best embodiment thereof;

but we desire to have it understood that the apparatus shown is only illustrative, and that the invention may be carried out by other means.

What we claim as new and desire to secure by Letters Patent of the United States, 1s

1. The combination is a system of motor control of two electromagnetic switches, a relay for controlling the second of said switches having a switch member biased to one position and movable under the control of the motor current to a second position to energize the second switch to close after the closing of the first switch, and an electromagnet forming a part of the said relay which is energized in the second position of the switch member for holding the said switch member in the second position.

2. The combination in a system of motor control of two electromagnetic switches, and a relay having a switch member under the control of the first switch for controlling the second switch, the said relay having electromagnetically controlled means for biasing the switch member to one position, for releasing the switch member to move under the control of the motor current to a second position to energize the second switch to close after the closing of the first switch, and for holding the switch member in the second position.

3. The combination in a system of motor control of two electromagetic switches, a switch member mechanically held in one position against its bias to a second position, electromagnetically controlled means energized responsively to the closing of the first switch for releasing the switch member to move under the control of the motor current to the second position to energize the second switch to close, and an electromagnet energized through the switch member in the second position for holding the switch memberin the second position. v

4. The combination in a system of motor control of two electromagnetic switches, a switch member mechanically held in one position against its bias to a second position, an electromagnet energized by the closing of the first switch for releasing the switch memher to move to its biased position under the control of the motor current to energize the second switch to close, and an electromagnet for holding the switch member in the second position energized through a shunt circuit to the first electromagnet which includes the switch member in the second position.

5. The combination in a system of motor control of two electromagnetic switches, a switch member mechanically held in one position against its bias to a second position, an electromagnet energized by the closing of the first switch for releasing the switch mem her to move to its biased position under the control of the motor current to energize the second switch to close, an electromagnet for holding the switch member in the second position energized in the second position of the switch member through a shunt circuit to the first electromagnet, and means whereby when the second switch is closed it is maintained energized through a circuit independentof the switch member and the said electromagnets are deenergized.

6. The combination In a system of motor control of two electromagnetic switches, a relay having a switch member held in one position against its bias to a second position for controlling the second of said switches, the said relay having a releasing electromagnet, a controlling electromagnet energized in accordance with the motor current and a holding electromagnet for said switch member, and connections whereby when the first of said switches is closed, the said releasing electromagnet is energized to release the switch member to move in accordance with its bias to the second position under the control of the said controlling electromagnet to energize the second of said switches to close, and the said holding electromagnet is energized in the second position of the switch member to hold the same in the second position.

7. The combination in a system of motor control of two electromagnetic switches, a relay having a switch member mechanically held in one position against its bias to a second position for controllingthe second of said switches, the said relay having a releasing electromagnet, a controllin electromagnet energized in accordance with the current taken by the motor, and a holdin electromagnet for said switch member, an connections whereby when the first of said switches is closed, the said releasing electromagnet is energized to release the switch member to move in accordance with its bias to the second position under the control of the said controlling electromagnet to energize the second of said switches to close, the said electromagnet is energized in the second position of the switch member to hold the same in the second position until after the second of said switches closes, and the second of said switches is maintained closed through a circuit independent of the said switch member, and the said relay holdin electromagnet is deenergized when the said second switch is closed.

In witness whereof, LOUIS J. WEBER has hereunto set his hand this 24th day of March, 1921, and ERNEST C. GoooH has hereunto set his hand this 4th day of April, 1921.

LOUIS J. WEBER. ERNEST C. GOOCH. 

